BEIRUT - Syria's government and rebels accused each other of firing a rocket loaded with chemical agents outside the northern city of Aleppo on Tuesday, an attack which a cabinet minister said killed 16 people and wounded 86.President Bashar al-Assad, battling a two-year uprising against his rule, is widely believed to have a chemical arsenal.US President Barack Obama, who has resisted overt military intervention in Syria's two-year-old civil war, has warned Assad that any use of chemical weapons would be a "red line".Washington has also expressed concern about chemical weapons falling into the hands of militant groups - either hardline Islamist rebels fighting to topple Assad or his regional allies.Zoabi said 16 people were killed and 86 wounded - many of them critically - in the attack which he said was launched from Aleppo's southeastern district of Nairab towards Khan al-Assal.He said Turkey and Qatar, which have supported rebels, bore "legal, moral and political responsibility" for the strike.Saadeddine, a spokesman for the Higher Military Council in Aleppo, said the rebels had not carried out the attack."We were hearing reports from early this morning about a regime attack on Khan al-Assal, and we believe they fired a Scud with chemical agents," he told Reuters by telephone from Aleppo."Then suddenly we learned that the regime was turning these reports against us," he said. "The rebels were not behind this attack." Two weeks ago rebel fighters seized a police academy in Khan al-Assal, about eight km (five miles) southwest of Aleppo, which was being used as an artillery base by Assad's troops.But the Syrian Observatory for Human Rights, which monitors the conflict using a network of contacts in Syria, said Assad's forces had since retaken at least part of the town.In the capital Damascus, activists released video footage on Tuesday showing men and boys lying in a medical centre, all of them receiving oxygen, in the aftermath of what they said was a separate chemical attack.They gave no details or casualty toll for what they said was an attack in Otaiba, east of Damascus. Like other videos and activist reports, it could not be independently verified.One boy in a light blue sweater lay apparently unconscious on a medical bed with mucus around his mouth and nose. A man was using a suction tube to remove the mucus from inside his nose and the boy twitched.Syrian officials have neither confirmed nor denied this, but have said that if it existed it would be used to defend against foreign aggression, not against Syrians. There have been no previous reports of chemical weapons in the hands of insurgents.Information Minister Omran al-Zoabi said rebels fired a rocket with chemical weapons at the town of Khan al-Assal, southwest of Aleppo, in what he called a "dangerous escalation".But a senior rebel commander, Qassim Saadeddine, denied the accusation and said he believed forces loyal to Assad had fired a Scud missile carrying chemical agents.